Fungi of Extreme Environments

Abstract

The majority of fungi are mesophiles, and grow at temperatures in the range of 5-35°C with optimum temperatures for growth between 25 and 30°C. Fungi exist, however, which grow very well outside the mesophilic temperature range; some are cold-tolerant (psychrotolerant) and are capable of growth near or below 0°C, while others are heat-tolerant (thermotolerant) and grow above 40°C. Many thermotolerant fungi grow over most of the mesophilic range but others are so highly adapted to growth in hot conditions that they can grow only at relatively high temperatures. These are the so-called thermophiles (heat-lovers) with high optimum temperatures for growth, and defined by Cooney and Emerson (1964) as those fungi unable to grow below 20°C. Similarly, among psychrotolerant species psychrophiles exist with low maximum and optimum temperatures for growth (Table 12.1). While dividing fungi into different groups with respect to tolerance of temperature extremes is useful to distinguish between the physiological behaviour of different species, these divisions are rather arbitrary and are, of course, quite artificial since psychrophiles, mesophiles, etc. are all part of a continuum of response to temperature by fungi. 12.1.1 Thermotolerant and thermophilic fungi Thermotolerant and thermophilic fungi are common in large, well-insulated, damp heaps of plant materials where the waste heat from microbial metabolism becomes trapped, causing the internal temperatures of the heap to rise in a self-heating (thermogenetic) process. A commonplace situation where heat-tolerant fungi thrive is in garden compost heaps. Piling plant debris into heaps is a simple but effective way of raising N. J. Dix et al., Fungal Ecology © Neville J Dix and John Webster 1995